The present invention relates to busway type electrical distribution systems. More specifically, the present invention relates to a water-resistant busway with a water drainage duct.
Electrical busways have long been used to transmit multi-phase, high-current electrical power. Busways generally consist of long, rectangular bus bars of copper or aluminum material disposed within a housing. The housing generally comprises a metal top plate, bottom plate, and side plates attached to each other forming an elongated parallelepiped of rectangular cross section. Each side plate of the housing extends above the top plate and below the bottom plate, forming top and bottom flanges extending along the length of the housing.
Modern busways are designed in modular form, with a busway system comprising a series of standard straight lengths, elbows, turns, offsets, and tees connected to each other electrically and mechanically by joints. To form the electrical connection between adjoining busway sections, the joints employ electrically conductive splice plates that slidably engage the bus bars of each adjoining section. The splice plates and bus bars are held together by one or more insulated joint bolts that pass through the splice plates and compress the splice plates onto the bus bars.
Busway housings for use outdoors are designed to prevent the ingress of rain, condensation, and melting snow which is deleterious to internal portions of the busway and can cause an electrical short. Typically, the housing for each section is sealed along the top and sides, with the bus bars extending from the ends of the housing so that they may be attached to the joint. Once the joint and adjoining sections have been connected, a joint cover is attached to complete the water-resistant housing. The joint cover provides water resistance to the joint itself, the joint bolt(s), and the unprotected ends of each section attached to the joint. The joint cover is attached to the joint housing by a plurality of screws.
During installation of the outdoor busway, the technician must bolt the joints and adjoining sections together with the joint bolt(s), then screw the water-resistant joint cover onto the joint. Similarly, during maintenance, the technician must unscrew and remove the joint cover to inspect and re-tighten the joint bolt(s). Unfortunately, the attachment and removal of the joint cover increases the time to install and perform maintenance on the busways and can lead to increased expenses due to stripped or lost screws.
To reduce maintenance time, inspection holes have been placed in the joint cover. This allows the technician to inspect and re-tighten the joint bolts without removing the joint cover. A plug is placed in the inspection hole to prevent water from entering when maintenance is not being performed. The plug comprises an elastomeric portion with a bolt disposed through its center. The plug is placed in the hole and the bolt tightened to compress the elastomeric portion axially so that it expands radially to plug the hole. The plug provides an improvement over having to remove the entire joint cover. However, tightening the plug increases time to perform maintenance and can lead to increased expense if these relatively expensive plugs are lost or destroyed. In addition, the access hole must be round in shape because of the type of plug used. This requirement places a limitation on design flexibility.
Outdoor busways are also designed to drain water that may accumulate on the outside of the housing. Water allowed to accumulate and stand on the external portion of the housing can be deleterious to the housing. This is especially important for the top of the housing where the top flanges and the top plate create a channel where water can be trapped. Typically, weep holes are drilled in the top flanges to drain water from the top of the housing. Unfortunately, the construction of the housing prevents the weep holes from being located so that they are flush with the top plate, nor can the holes be placed close to the joints. Therefore, there are locations on the housing where water will accumulate.